Psychiatrists call it "mass hysteria," ie "the manifestation of the same hysterical symptoms by more than one person." And throughout history, there have been a number of fascinating examples of the phenomenon. These "psychogenic illnesses" are referred to in terms of "outbreak" and "spread," just like any biological contagion, but the results vary from low-grade "moral panics" on one end of the spectrum (eg, McCarthyism and witch purges) to the most outlandish fits of behavior on the other. Here are some of our favorite examples of the latter.

The Dancing Plague of 1518

One of the deadlier outbreaks of mass hysteria, the so-called "dancing plague" broke out in the French city of Strasbourg when a woman named Troffea began to dance uncontrollably in the street -- for days on end. By the end of the first week, several dozen people had joined her, and by the end of a month, up to four hundred were dancing. Of course, they couldn't keep this up forever, and most eventually died from heart attack, stroke or exhaustion.

Even stranger, dancing outbreaks were common in Europe between the 14th and 18th centuries. Referred to as "St. John's Dance," sufferers were thought to be possessed by the Devil, and the "plague" was considered contagious by sight. Some historians believe that socio-economic factors may have been to blame in some of these "plagues," especially the 1518 outbreak: John Waller writes that "famine had been prevalent in the region for some time, caused by very cold winters, very hot summers, crop frosts, and violent hailstorms. Mass deaths followed from malnutrition, and those who survived were forced to kill their farm animals, take out loans, and perhaps even beg in the streets. In addition to food shortages, diseases such as smallpox, syphilis, leprosy, and "the English sweat" (a new disease) afflicted the populace."

The Monkey Man of New Delhi

Witnesses in New Delhi called it "Monkey Man." According to reports circulating around the Indian capitol in the summer of 2001, people were being attacked in the night by a strange, four-foot monkey-like creature which bit, scratched and frightened the heck out of its victims. Often inconsistent in their details, eyewitness descriptions variously characterized the Monkey Man as sporting a thick coat of black hair, a metal helmet, sharp, artificial claws, glowing red eyes and even glowing buttons -- as in electronic ones -- on its chest. All this confusion led to the release of two different, but equally absurd, police sketches, pictured:
Monkey_Man.jpg

According to Wikipedia and several Indian newspapers,

Many people reported being scratched, and two (by some reports, three) people even died when they leapt from the tops of buildings or fell down stairwells in a panic caused by what they thought was the attacker. Theories on the nature of the Monkey Man ranged from an avatar of a Hindu god, to an Indian version of Bigfoot, to a cyborg that could be deactivated by throwing water on the motherboard concealed under fur on its chest. The news website Ananova reported in June 2001 that the Monkey Man was last seen boarding an Aeroflot flight to Moscow ("Monkey Man reappears on Moscow-bound flight"). The story was also carried by the Russian newspaper Pravda ("Monkey Man Attacks Russian Airliner").

So what happened? No "Monkey Man" was ever photographed or captured, and the furor eventually died down. The scratches sustained by victims were considered most likely to have been caused by cats, rats or small monkeys. At odds with newspaper stories, an official psychiatric report suggested that victims' injuries were mostly blunt and probably originated from accidents in the dark. Illiterate rural immigrants, a high level of superstition, and the fact that much of the population slept in the streets and on roofs well within the reach of real monkeys probably all contributed to what was most likely an example of collective hysteria.

The Tanganyika Laughter Epidemic

While this story is somewhat apocryphal, it's not beyond belief. Here's what supposedly went down in a small Tanzanian village in 1962:

The epidemic seems to have started within a small group of students in a boarding school, possibly triggered by a joke. Laughter, as is commonly known, is in some sense contagious, and for whatever reason in this case the laughter perpetuated itself, far transcending its original cause. Since it is physiologically impossible to laugh for much more than a few minutes at a time, the laughter must have made itself known sporadically, though reportedly it was incapacitating when it struck. The school from which the epidemic sprang was shut down; the children and parents transmitted it to the surrounding area. Other schools, Kashasha itself, and another village, comprising thousands of people, were all affected to some degree. Six to eighteen months after it started, the phenomenon died off.

But is such a thing even possible? On a much smaller scale, it's a phenomenon all of us have witnessed; with a little extrapolation, it's not tough to imagine a 6-month bout of infectious laughter. In case any of you don't know what we're talking about, here's a great example from YouTube, of an otherwise lame comedy routine made great by infectious, incapacitating laughter: